Phytosterols are naturally occurring plant sterols in which the C5-C6 bond is saturated. Thus, while sitostanol bears a double bond at this position, sitostanol has a single bond. Sitostanol is almost completely unabsorbable by the intestine and also reduces the absorption of cholesterol. The cholesterol-lowering effect of sitostanol is increased by converting it to fatty acid esters. In studies conducted in Finnish hypercholesterolemic subjects, plant stanol esters (PSE) have shown decreases in total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) of 6 to 11% and 9 to 14%, respectively. The diet of Finnish research subjects was higher in total fat, saturated fat, and cholesterol than the typical American diet. It is important to determine if a diet lower in total and saturated fat, the Step I Diet, and PSE together will result in LDL-C lowering that exceeds either treatment alone. The purpose of this randomized controlled 6-week study is to: 1) determine if there are differences among four treatment groups (usual diet, usual diet + PSE, Step I Diet, Step I Diet + PSE), 2) to quantify changes that may occur in lipoprotein composition of very low density lipoprotein (VLDL), LDL-C, high density lipoprotein (HDL), and appropriate subfractions of subjects incorporating PSE into their usual diets or the Step I Diet, and 3) to determine the time dependence of changes in level of lipids and lipoproteins.